/Engine/Source/Editor/UnrealEd/Public/EditorModeRegistry.h
Registers an editor mode type. Typically called from a module's StartupModule() routine.
template<class T> void RegisterMode ( FEditorModeID ModeID, [FText](API\Runtime\Core\Internationalization\FText) Name, [FSlateIcon](API\Runtime\SlateCore\Textures\FSlateIcon) IconBrush, bool bVisible, int32 PriorityOrder )